Melt the butter in a large, deep skillet. Add the onion, celery, red and green bell peppers and garlic and cook over moderately high heat, stirring, until softened, about 5 minutes. Add the livers and ground pork and cook, stirring, until the livers are browned on the outside, about 5 minutes. Stir in the wild and long-grain rice, chicken stock, thyme, bay leaves and 1 teaspoon of salt and bring to a boil. Cover and cook over low heat until the long-grain rice is tender, about 20 minutes. Discard the bay leaves. Season the dirty rice with salt, pepper and Tabasco and stir in the chopped scallions. Transfer the rice to a bowl, fluff with a fork and serve.